1. Field of the Invention
The present invention relates to a combustion apparatus in which a burner of combustion means is monitored and the supply of air thereto is adjusted and controlled, and a method for combustion control thereof.
2. Description of the Related Art
Conventionally, in a combustion apparatus, occurrence of going out of flame during halfway combustion and incomplete combustion for some reason is monitored, and control is performed that the supply of fuel or air is adjusted so as to perform combustion operation with proper air-fuel ratio. For monitoring condition of combustion, a thermocouple, a detector that detects the level of CO in exhaust and detection of flame current by a flame rod are used, for example.
As an apparatus for processes of monitoring and adjusting condition of combustion like the above, for example: a thermocouple is used, a thermal time constant of the thermocouple is stored when the apparatus is used, and correcting means predicts a steady-state value of the thermocouple by a time constant to output the value for an output change of the thermocouple according to the change of the condition of combustion; the predicted value is compared with a setting value of condition setting means, and air supply control means is controlled to increase or decrease the supply of air according to positive and negative deviations and the level thereof (for example, Japanese Laid-open Patent Publication No. 07-004639).
There is also an apparatus that: a detected value of the level of CO in exhaust by a CO sensor is compared with a reference value of the level of CO corrected according to the amount of combustion gas to judge incomplete combustion; if an integrated value obtained from deviation of the reference value and the detected value exceeds a safety limit, an alarm is issued, operation is stopped and reuse of the apparatus is allowed (for example, Japanese Laid-open Patent Publication No. 05-026438).
There is a combustion implement in which: occurrence of a deficiency of operating conditions such as a suction air blockage and an abnormal drop of an air supplying function of a blower, an exhaust blockage due to a damage of an exhaust cylinder to be connected to a port and adherence of unburned carbon to fins of an exchanger, and damage of a chamber due to heating is detected via a pressure of the chamber; abnormality is decided and the operation is inhibited etc. (for example, Japanese Laid-open Patent Publication No. 06-011139).
There is an art: each of a first burner and a second burner is provided with first and second flame rods; flame sensing currents is sensed individually, and then the rotation of a fan is controlled according to condition of combustion; air volume variable control is preferentially carried out as to the second burner (for example, Japanese Laid-open Patent Publication No. 06-323532).
In monitoring of combustion of a burner disposed in a combustion apparatus, there is a problem that when a thermocouple is used, for example, the thermocouple cannot react to a sudden change of air-fuel ratio because there occurs a delay in response until the thermocouple is heated, and cannot react to abnormal heating, blow-out of flame, a backfire, etc. There is also an apparatus of executing correction by expectancy in order to react to such response. However, there is a limit on increasing the response speed by expectancy while accurate monitoring control is maintained.
In combustion monitoring using a CO sensor and a pressure sensor, a circuit and a control unit for monitoring are needed individually. Thus, structure therefor must be complicated and the number of components must be increased.
Further, in a combustion apparatus providing a plurality of kinds of burners, components are increased and a control process is complicated for disposing monitoring means in each of the burners.
Concerning such problems, there is no disclosure or suggestion thereof in Japanese Laid-open Patent Publications Nos. 07-004639, 05-026438, 06-011139 and 06-323532, and no disclosure or suggestion about the structure etc. for solving them is presented.